ARTICLES
Chinese Science Bulletin
© 2008
SCIENCE IN CHINA PRESS
Springer
Geochemical character and material source of
sediments in the eastern Philippine Sea
XU ZhaoKai1,2,3,4, LI AnChun1†, JIANG FuQing1 & XU FangJian1,4
1
Based upon analyses of grain-size, rare earth element (REE) compositions, elemental occurrence
phases of REE, and U-series isotopic dating, the sediment characteristics and material sources of the
study area were examined for the recently formed deep-sea clays in the eastern Philippine Sea. The
analytical results are summarized as follows. (1) Low accumulation rate, poor sorting and roundness,
and high contents of grains coarser than fine silt indicate relatively low sediment input, with localized
material source without long distance transport. (2) The REE Contents are relatively high.
Shale-normalized patterns of REE indicate weak enrichment in heavy REE (HREE), Ce-passive anomaly,
and Eu-positive anomaly. (3) Elemental occurrence phases of REE between the sediments with and
without crust are similar. REE mainly concentrate in residual phase and then in ferromanganese oxide
phase. The light REE (LREE) enrichment, Ce-positive anomaly, and Eu-positive anomaly occur in residual phase. Ferromanganese oxide phase shows the characteristics of relatively high HREE content
and Ce-passive anomaly. (4) There are differences in each above mentioned aspect between the sediments with and without ferromanganese crust. (5) Synthesizing the above characteristics and source
discriminant analysis, the study sediments are deduced to mainly result from the alteration of local and
nearby volcanic materials. Continental materials transported by wind and/or river (ocean) flows also
have minor contributions.
sediment, grain-size, rare earth elements, discriminant function, elemental occurrence phase, material source, eastern Philippine Sea
The Philippine Sea is the largest marginal sea in the
West Pacific. The Philippine Sea Plate is located between the Eurasia Plate and the Pacific Plate, the largest
continental and oceanic plate on the earth, respectively.
The geologic setting is, therefore, unique and special,
with great depth in average of deeper than 6000 m,
complex crustal structure, and rough seabed topography.
These factors all lead to the improvement of research
difficulty on it. So far, a systematic research on the surface sediments of this area has been rather rare, which is
extremely off-balanceable to its crucial structural position[1]. The recent discovery of new-type deepwater ferromanganese crusts on surficial seabed necessitates the
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research on sediment characteristics and material
sources for recently formed sediments[2,3]. This is not
only helpful in revealing the formation mechanism of
new-type ferromanganese crusts, but also in understanding the transport and sedimentation of fine-grained
substances carried by the East Asian monsoon, especially the East Asian winter monsoon[4].
Received August 10, 2007; accepted December 13, 2007
doi: 10.1007/s11434-008-0118-7
†
Corresponding author (email: [email protected])
Supported by the Key Program of the National Natural Science Foundation of China
(Grant No. 90411014), the National Major Basic Research and Development Project
(Grant No. 2007CB815903), the National Natural Science Foundation of China
(Grant Nos. 40576032 and 40506016), and the Brain Korea 21 Program (Modern
Sedimentation on the Yellow and East China Sea) of Korea
Chinese Science Bulletin | March 2008 | vol. 53 | no. 6 | 923-931
OCEANOGRAPHY
Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071,
China;
2
Department of Oceanography, Kunsan National University, Kunsan 573701, Republic of Korea;
3
Yantai Institute of Coastal Zone Research for Sustainable Development, Chinese Academy of Sciences, Yantai 264003, China;
4
Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Sun et al.[5], Piper[6], and Huang et al.[7] demonstrated
that grain-size, REE compositions, and elemental occurrence phases of REE were useful research aspects in
reflecting the sediment origins and material sources of
deep-sea sediments. Furthermore, the U-series isotopic
chronology has been proved to be one of the most effective and common dating methods for recently formed
sediments with low accumulation rate and scarce fossil[8,9].
The present work aims to reveal the grain-size and
geochemical characteristics of REE, and then interpret
the origins and material sources of recently formed clays
in the eastern Philippine Sea.
1 Materials and methods
The present study area is located in the northern Parece
Vela Basin of the eastern Philippine Sea (Figure 1(a))[2],
mostly below the carbonate compensation depth of about
4000―4500 m[10]. The sediments, therefore, contain very
few calcareous debris and other organisms (e.g., spongy
spicule and diatom).
Sediment samples were collected with box sampler
and gravity corer during 4 cruises of R/V Science No. 1
(Figure 1(b)). After the measurement on pH and Eh values of the tops (0―2 cm) by potential method, sediment
samples were freezed for subsequent analyses.
Smear identification was carried out under polarizing
microscope and binocular microscope with a magnification factor of 200―400 times. The relative percentages
of calcareous organisms (foraminifera and coccolithes),
siliceous organisms (radiolarian and diatom), volcanic
materials (volcanic glass and volcanic debris), terrigenous
substances (quartz, feldspar, hornblende, epidote, etc.),
and authigenic minerals (mainly composed of authigenic
ferromanganese micro-nodules or debris) were estimated
with the eyeballing estimation method. And then the
sediment type could be ascertained according to the
naming principle for deep-sea sediments.
Grain-size analysis was completed with Cilas 940L
instrument. The measurement scope was 0.3―2000 μm
with resolution at 1/4Φ interval.
For the REE analysis, sediment samples were dried at
50℃ and then powdered to below 200 meshes. The
powdered samples were measured in the Central Laboratory, Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences
924
with Inductively Coupled Plasma-Mass Spectrometer
(ICP-MS) in precision below 4%.
As to the elemental occurrence phase research on
sediment, although there have been some attempts reported already[7,11], similar research on deep-sea sediments remains limited. Here we used a 5-steps chemical
extraction method, that is, the bulk compositions were
divided into adsorption, carbonate, ferromanganese oxide,
organic, and residual phase with different reagents[2]. The
REE contents in each phase were measured with
ICP-MS in the National Research Center for Geoanalysis, Chinese Academy of Geological Sciences with precision better than 3%.
U-series chronology was got from short core sediment collected just beneath the ferromanganese crust,
using Octete Plus 8-channel Alpha Spectrometer in the
U-series Laboratory, Institute of Geology and Geophysics, Chinese Academy of Sciences. The radioactivities of
230
Th and 234U from eight sub-samples were measured in
precision within 5%.
2 Results and discussion
2.1 Smear identification and sediment classification
Based on the smear identification under microscope, 314
sediment samples can be classified into 11 types:
deep-sea clay (79.0%), siliceous ooze (5.7%), claybearing siliceous ooze (4.1%), clayey siliceous ooze
(3.5%), siliceous clay (2.9%), silica-bearing clay (2.2%),
clayey calcareous ooze (0.6%), clay-bearing calcareous
ooze (0.6%), calcareous ooze (0.6%), silica-bearing calcareous clay (0.3%), and calcareous clay (0.3%). The
deep-sea clay is the main sediment type and most of the
new-type ferromanganese crusts were found to accrete
on the surface of deep-sea clays. And then following
analyses and discussion are only focused on the
deep-sea clays.
2.2 Sedimentary environment and accumulation
rate
Eh and pH values of sediment directly reflect the environmental conditions. The sediments are characterized
by slightly oxidative (average Eh value of 111.9) and
alkalescent (average pH value of 7.44) conditions. Besides, the sediments with ferromanganese crust always
have relatively higher Eh values than the sediments
without crust (average of 123.1 and 110.7, respectively),
indicating the relatively stronger oxidizing conditions of
XU ZhaoKai et al. Chinese Science Bulletin | March 2008 | vol. 53 | no. 6 | 923-931
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OCEANOGRAPHY
Figure 1
Geologic map showing the study area (a) and location of sediment samples (b).
XU ZhaoKai et al. Chinese Science Bulletin | March 2008 | vol. 53 | no. 6 | 923-931
925
the sediments with ferromanganese crust[2].
Reportedly, the 230Thexcess (230Thex) dating method is a
high precision tool in geochronology for recently formed
sediments with low accumulation rate and fossilpoverty[8,9]. The calculation formula is
(1)
ln230Thex (h) = −λh/v+ln230Thex (0),
230
230
where Thex (h) and Thex (0) are the radioactivity intensity of 230Thex at depth of h and the surface, respectively; λ is a decay constant. From the 230Thex data, a
growth rate curve in slop of k is obtained, and the average accumulation rate can be calculated from v = −λ/k.
Therefore, the age can be determined from t = h/v. The
230
Thex dating data on short core sediment under the ferromanganese crust (8.5 cm, 5400 m, 16°31.21′N,
137°19.64′E; Figure 1(b)) are listed in Table 1. The
234 238
U/ U values of sub-samples change between 1.00
and 1.08, very close to 1, reflecting the equilibrium state
between 234U and 238U in sub-samples. This satisfies the
precondition for a U-series dating on sediments[8,9]. Besides, the 230Thex values of sub-samples decrease exponentially and regularly with depth (Table 1; Figure 2),
indicating that these data are applicable for sediment
dating. The average accumulation rate is calculated to be
only 1.38 mm/Ka, which corresponds to an accumulation period of about 61.5 Ka for the study core.
Table 1 U-series dating results of short core sediment beneath the ferromanganese crust
230
230
Thex
Depth
Weight
Th
234
234
U/238U
U (dpm/g)
(dpm/g)
(cm)
(g)
(dpm/g)
0―0.5 2.0379 1.08±0.07 1.16±0.05 0.88±0.05 0.28±0.07
0.5―1.5 2.0276 1.00±0.11 1.08±0.04 0.81±0.07 0.27±0.08
1.5―2.5 1.8092 1.03±0.08 1.05±0.04 0.81±0.05 0.24±0.06
2.5―3.5 1.8380 1.02±0.11 1.16±0.04 0.97±0.08 0.19±0.09
3.5―4.5 2.2456 1.04±0.09 1.00±0.05 0.79±0.05 0.21±0.07
4.5―5.5 2.0244 1.04±0.07 1.12±0.05 0.93±0.05 0.19±0.07
6.5―7.5 1.1832 1.03±0.08 1.15±0.12 0.97±0.06 0.18±0.02
7.5―8.5 2.0723 1.01±0.06 1.03±0.04 0.86±0.04 0.17±0.06
The accumulation rate is one or two orders of magnitude lower than the Late Pleistocene-Holocene sediments in the marginal seas of the East China Sea and the
South China Sea[12,13], and also in the West Pacific Warm
Pool[14]. The accumulation rate is equal to the Late Cenozoic sediments in the Clarion-Clipperton area of the East
Pacific, where ferromanganese nodules are enriched[7]. It
is considered that the lower accumulation rate and relatively stronger oxidizing conditions are both favorable for
the formation and accretion of new-type deepwater ferromanganese crusts in the present study area.
926
Figure 2 Depth profile of
romanganese crust.
230
Thex of short core sediment under the fer-
2.3 Grain-size composition
Grain-size distribution of clastic sediments is an important fabric feature in tracing the material source, transport and deposition process ever occurred, and sedimentary condition[5].
Based on the Folk-Ward’s grain-size classifications[15],
sediment samples mainly belong to the types of silty
clay-clayey silt or clayey silt-silt (Table 2), whose
grain-size distribution characteristics are generally similar. The average mean size is in fine silt grade, with average sorting of 1.49Φ (Table 2). The sediments are finer
but slightly better in sorting than the surface sediments
in the Okinawa Trough and the South China Sea[16,17]. It
can be deduced that the sediments in the study area are
less affected by the direct input of terrigenous materials
from the continents nearby.
Table 2 Summary of major grain-size parameters of surface sediments
Deep-sea
Change
Mean Sorting Sand
Clay
Silt (%)
clay
range
(Φ)
(Φ)
(%)
(%)
minimum
6.67
1.24
0.00
38.52 20.14
With crust
maximum 8.29
1.92
7.59
79.37 61.48
(31)
average
7.51
1.44
0.38
62.57 37.06
minimum
6.27
0.10
0.00
0.15
0.00
Without
maximum 8.34
2.11
14.03
100.00 99.85
crust (218)
average
7.78
1.50
0.27
52.63 47.09
Total (249) average
7.75
1.49
0.28
53.87 45.85
The average content of grains coarser than silt is
54.15%. These grains are generally poor in roundness
under microscope. Combining the poor sorting (generally higher than 1), we can know the localized material
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2.4 Geochemistry of REE
REE is a good geochemical tracer for the material
source, sedimentary environment, deposition process,
and is also focused on the present study, together with
Ce-anomaly as an indicator for paleo-redox condi―
tions[6,22 24].
2.4.1 REE content and distribution pattern.
From
the 15 elements of REE measured in this study, the anterior 6 elements (La, Ce, Pr, Nd, Sm, Eu) are called by a
joint name of LREE, expressed by ΣCe; the remaining 9
elements (Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) have a
general name of HREE, represented by ΣY. The total
REE amount is denoted as ΣREE[25].
The ΣREE contents range between 163.89 μg/g and
468.26 μg/g, with an average of 270.91 μg/g (Table 3),
which are generally higher than Chinese loess and the
Okinawa Trough sediments, but lower than the Middle
Pacific pelagic sediments. In addition, the ΣCe/ΣY ratios
are 1.41―3.17, with an average of 1.90, within the
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range of the above two types of regions also.
Table 3 Analysis results of REE for samples in the study area and related areas
Change
ΣREE
Area
Sample
ΣCe/ΣY δ Cea) δ Eub)
range
(μg/g)
deep-sea
minimum
239.77
1.41
0.54 1.02
l
i h maximum
468.26
2.27
1.03 1.12
average
307.93
1.82
0.77 1.08
deep-sea
minimum
163.89
1.42
0.45 1.00
Eastern
Philippine l
maximum
310.99
3.17
1.03 1.19
Sea
average
240.83
1.96
0.82 1.07
total
deep-sea
average
270.91
1.90
0.79 1.07
clays (29)
surface
Okinawa
average
124.53
2.43
0.99 0.67
sediTrough
ments[26,27]
China
loess[28]
average
171
3.56
1.41 0.98
surface
Middle
average
415.36
1.81
0.88 0.98
sediPacific
ments[29]
Mariana
66.43
0.99
0.91 1.52
basalts[30] average
Trough
*
*
a) δ Ce=Ce/Ce =2CeSN/(LaSN+PrSN), b) δ Eu = Eu/Eu = 2EuSN/(SmSN +
GdSN), SN is shale-normalization.
Shale-normalized patterns of REE show rather consistent characteristics of weak HREE enrichment, Cepassive anomaly, and Eu-positive anomaly (Figure 3).
The character of weak HREE enrichment displays a
clear difference from the Okinawa Trough sediments,
but is closer to the Middle Pacific sediments (Figure 3),
which is possibly caused by the following reasons.
Firstly, sediment materials are dominantly derived from
the nearby volcanic materials enriched in HREE[31].
Secondly, the formation of ferromanganese crust has
obstructed the alteration of underlying sediments, and
has a strong sorption of LREE from seawater, especially
for Ce[2,3,25]. Thus, it leads to the relative enrichment of
unaltered volcanic materials, ΣY, and ΣREE in underlying sediments. This can also be attested by the higher
Figure 3 Shale-normalized patterns of REE for surface sediments in the study area and related regions.
XU ZhaoKai et al. Chinese Science Bulletin | March 2008 | vol. 53 | no. 6 | 923-931
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OCEANOGRAPHY
sources from the alteration of nearby volcanic materials
without serious collisions and abrasions during transport,
whereas terrigenous materials of eolian transport (very
uniform and mainly composed of fine fractions finer than
10 μm) are minor in amounts[18]. This is also consistent
―
with the geographic location of the study area[19 22].
In addition, the coarser grains are more abundant in
the sediments with crust than the sediments without
crust (Table 2). This implies that the formation of ferromanganese crust does not favor the accumulation of fine
clayey materials of eolian loess from upper seawater
into the underlying sediments. Although the grain-size
characteristics are almost similar between the sediments
with and without crust due to their similar geologic
background, differences might have occurred by the
formation and accretion of ferromanganese crust.
ΣREE values while lower ΣCe/ΣY ratios of the sediments with crust than the sediments without crust.
Among all the possible sources, only the nearby basalts have characteristic Eu-positive anomalies, whereas
the others are all neutral or Eu-passive anomalies (Table
3). Therefore, the Eu-positive anomaly character in the
present sediments should be interpreted as the sediment
materials derived from nearby volcanic sources.
Ce is usually depleted in the oceanic basin due to its
rapid accumulation in continental sediments during the
―
alteration process[32 34]. In addition, Ce is the only REE
that can be transformed with redox conditions in marine
environment. In the ocean, Ce2+ is extremely inclined to
be oxidized to Ce4+ and deposits directly into the ferromanganese crust. As a result, the oceanic ferromanganese crust always has Ce-positive anomaly, while other
biological and chemical deposits would show Ce-passive anomalies similar to seawater[2,3,25]. The Ceanomalies vary 0.45―1.03, with an averages of 0.79,
indicating that Ce is strongly depleted. This may also be
caused by the following reasons from two aspects.
Firstly, the sediments are mainly originated from the
alteration of nearby volcanic materials by bottom seawater, the sediments are, therefore, likely to inherit the
REE characteristics of seawater, while Ce-passive
anomaly is the most typical REE distribution character
of seawater. Secondly, since the ferromanganese crust
prefers adsorbing Ce from seawater[2,3,25], Ce might be
depleted within the underlying sediments. This explanation is clearly supported by the stronger Ce-passive
anomalies of the sediments with crust than the sediments
without crust.
2.4.2 Sediment source discrimination.
Aluminum
element in marine sediments mostly exists in aluminosilicate minerals of terrigenous origin and is relatively
stable in the sedimentation process, but is not involved
in biological medium in general. Hence, the element
normalization to Al can be used to study the material
source and elemental change in marine environment,
compensating the influence of mineralogy and grain-size
Table 4
DF=(C1x/C2x)/(C1l/C2l)−1,
(3)
where (C1x/C2x) is the ratio of concentrations of element
1 and element 2 in the sediments, (C1l/C2l) is the ratio of
contents of element 1 and element 2 in the possible
sources. The absolute value of DF below 0.5 is generally
accepted as indicating a close relationship in material
origination. The smaller DF value, the closer relationship. In order to reflect the proximity more effectively
with DF, elements of similar chemical properties, especially the mobility, should be paired up. The chemical
properties of REE are very close to each other, and then
REE can be used for the DF calculation. For nearby
EFs of REE for surface sediments in the study area and the Okinawa Trough
Deep-sea clay
With crust (13)
Without crust (16)
Total (29)
Okinawa Trough[26,27]
928
effect[2]. The enrichment factor (EF) for a certain element (E) is calculated by the relative ratio to its average
abundance in the Crust as follows:
(2)
EF=(E/Al)sediment/(E/Al)crust.
When EF is close to 1, the element is considered to be
a Crust origin, whereas when EF is much higher than 1,
it will be deduced as a non-Crust source[35]. EFs of REE
for surface sediments in the study area and the Okinawa
Trough are listed in Table 4.
Most of the REE EFs exceed the value of 1, and are
all much higher than the terrigenous sediments in the
Okinawa Trough, especially for HREE. It is very likely
that the terrigenous materials are not the main sources,
also matches the geographic location of the present
study area far away from the continent[19]. In contrast to
the higher anomalies of HREE, the LREE EFs are not
much higher than 1, indicating the minor input of terrigenous components. The relatively low EF of Ce is interpreted as the preferential adsorption of Ce to ferromanganese crust from seawater[2,3,25], resulting in the
lower EFs of Ce in the sediments under crust than the
sediments without crust.
To further discuss the material source, discriminant
function (DF) was applied to estimate the proximity to
possible sources, meaning the degree of similarity of the
study sediments to local and nearby volcanic materials,
sediments in the Okinawa Trough, and eolian Chinese
loess[36]. The formula used for DF calculation is
La
1.48
1.46
1.47
0.78
Ce
0.94
1.06
1.01
0.82
Pr
1.65
1.68
1.67
1.14
Nd
1.89
1.84
1.86
1.09
Sm
2.49
2.46
2.47
1.40
Eu
3.41
3.21
3.30
1.30
Gd
3.18
2.91
3.03
1.64
Tb
3.01
2.80
2.89
1.53
Dy
3.27
3.00
3.12
1.36
Ho
3.00
2.66
2.81
1.42
Er
2.84
2.60
2.71
0.99
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Tm
2.88
2.60
2.73
1.07
Yb
2.68
2.45
2.55
1.36
Lu
2.92
2.68
2.79
1.10
Y
2.97
2.50
2.71
1.37
Table 5 DF values of surface sediments
Terrigeneous sources
Deep-sea
clay
With crust
(13)
Without crust
(16)
Total (29)
Volcanic sources
West
Parece
Kyushy-Palau
Mariana
Vela
Ridge[31]
[31]
Ridge[31]
Basin
Loess[28]
Okinawa
Trough[26,27]
0.32
0.39
0.06
0.13
0.03
0.33
0.41
0.07
0.12
0.02
0.33
0.41
0.07
0.12
0.02
2.5 Elemental occurrence phase of REE
Elemental occurrence phases of REE by the wet chemical technique is accepted as being very significant for
the element origination, migration, transition, source,
related deposition environment, etc., in sediments[7,11].
The REE relative contents in different phases are
Table 6 REE relative percents in different phases of surface sediments
REE relative percent in different phases (%)
ΣREE
ΣCe
ΣY
Adsorption
0.1
0.1
0.1
Carbonate
1.6
0.8
3.8
With crust (2)
Ferromanganese
36.7
29.7
58.1
Organic
1.7
1.4
2.5
Residual
60.1
68.0
35.6
Adsorption
0.1
0.1
0.1
Carbonate
1.4
0.8
2.9
Without crust (1)
Ferromanganese
35.5
26.9
56.4
Organic
2.7
2.0
4.3
Residual
60.4
70.3
36.3
Adsorption
0.1
0.1
0.1
Carbonate
1.5
0.8
3.5
Total (3)
Ferromanganese
36.3
28.8
57.5
Organic
2.0
1.6
3.1
Residual
60.1
68.8
35.8
a) ΣCe/ΣY* is the ratio of ΣCe/ΣY in each phase and bulk.
Deep-sea clay
ΣCe/ΣY* a)
δ Ce
δ Eu
0.9
0.3
0.5
0.6
1.9
1.0
0.3
0.5
0.5
1.9
0.9
0.2
0.5
0.5
1.9
0.59
0.02
0.72
0.60
2.44
0.31
0.02
0.51
0.43
1.69
0.49
0.02
0.65
0.54
2.19
4.82
1.07
1.04
1.04
1.37
2.30
1.01
1.05
1.01
1.06
3.98
1.05
1.04
1.03
1.27
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listed in Table 6.
REE mainly concentrate in residual phase (60.1%)
and then in ferromanganese oxide phase (36.3%). The
REE contents in organic phase (2.0%) and carbonate
phase (1.5%) are very low, while negligible in adsorption phase (0.1%). In residual phase, the ΣCe/ΣY* value
(Table 6) is high enough to represent the relative enrichment of LREE to HREE, with obvious Ce-positive
anomaly. On the other hand, the relative depletions of
LREE and Ce in carbonate, ferromanganese oxide, and
organic phase all indicate the seawater origination of
these phases[23,24,37]. Eu is evidently enriched in adsorption phase and residual phase, while there are no obvious fractionations in other phases.
Though there is a clear difference among ΣREE between the sediments with and without crust, the shalenormalized patterns of each phase are similar (Figure 4),
so do characteristic parameters (Table 6) and changing
trends (Figure 4). This reflects the stable geologic background and material sources that control the REE concentration and enrichment for the study sediments regardless of the presence of ferromanganese crust[3,38].
Critical differences are, however, still present among the
sediments with and without crust, which are also relevant to the formation of ferromanganese crust.
Although REE mainly concentrate in residual phase
and ferromanganese oxide phase, there are still clear
differences between them. Residual phase is prone to
adsorbing LREE and thus shows the relative enrichment
of LREE to HREE and strong Ce-positive anomaly[24,33].
Moreover, residual phase of the sediments with crust
OCEANOGRAPHY
volcanic materials and sediments in the Okinawa Trough,
the HREE pair of Lu/Yb was used. As to eolian loess,
the LREE couple of Sm/Nd that is relatively stable in
the transport and deposition process was selected to be
mated. Table 5 shows the DF values of sediments to the
possible terrigenous sources and volcanic sources based
―
on Sm/Nd and Lu/Yb data[26 28,31]. The DF values of
three types of volcanic materials are very similar to each
other and are well below 0.5, meaning that the local and
nearby volcanic materials are the major material sources.
The DF values for Chinese loess and sediments in the
Okinawa Trough are relatively higher, which indicates
that continental materials from eolian loess and/or river
(ocean) flows are very low or have been greatly changed
during the long distance transport.
Figure 4 Shale-normalized patterns of REE in different phases of surface sediments.
always has a higher Ce-positive anomaly than the sediments without crust, which is related to the generally
stronger oxidizing conditions in the site of ferromanganese crust formation. Ferromanganese oxide phase tends
to enrich HREE from seawater, resulting in the depletion
of LREE to HREE and Ce-passive anomaly[7]. As for
Eu-positive anomaly in residual phase, it denotes its
high volcanic material compositions[7]. It can be deduced that the detrital materials in the sediments should
be mainly derived from volcanic materials on local and
nearby submarine ridges[7,31,34]. The strong Eu-positive
anomaly in adsorption phase (Table 6) might be caused
by the direct influence of alteration products of these
volcanic materials. This once more emphasizes the important contributions of local and nearby volcanic materials to the sediments.
3 Conclusions
Based on the comprehensive research and comparison of
grain-size, REE compositions, elemental occurrence
phases of REE, and U-series isotopic chronology, the
sediment characteristics and material sources were examined for the recently formed deep-sea clays in the
eastern Philippine Sea. The main conclusions we have
drawn are summarized as follows:
(1) The accumulation rate is very slow, only 1.38
mm/Ka, indicating very low sediment input. The relatively coarse grain-size, poor sorting, and poor roundness are considered to represent the localized character
of major material sources.
(2) The REE contents are relatively high. The REE
shale-normalized patterns of weak HREE enrichment,
Ce-passive anomaly, and Eu-positive anomaly are derived from the influence of alteration of volcanic mate1
930
Zang S X, Ning J Y. Interaction between Philippine Sea Plate (PH)
and Eurasia (EU) Plate and its influence on the movement Eastern
rials by bottom seawater.
(3) Elemental occurrence phases of REE between the
sediments with and without crust are generally similar,
which reflects the stable geologic background and material sources that control the REE formation and enrichment.
REE mainly concentrate in residual phase and also in
ferromanganese oxide phase. Residual phase is prone to
adsorbing LREE, and then the enrichment of LREE to
HREE and Ce-positive anomaly come into being. HREE
are relatively enriched in ferromanganese oxide phase,
which is caused by the preferential adsorption of HREE
to ferromanganese oxide phase. It also leads to the
Ce-passive anomaly in ferromanganese phase. Besides,
volcanic materials are responsible for the appearance of
Eu-positive anomaly in adsorption phase and residual
phase.
(4) Differences are usually found on grain-size and
REE geochemical characteristics between the sediments
with and without crust, which are caused by the formation of ferromanganese crust.
(5) Combining the above indices and source discriminant analysis, it is concluded that the study sediments are mainly derived from the alteration of volcanic
materials on local and nearby ridges. Terrigenous substances from the continents by either eolian loess and/or
river (ocean) flows have contributed in minor degree.
The authors would like to thank Professor Choi Jinyong of the Department
of Oceanography, Kunsan National University and Doctor Yu Roger of the
Chinese Journal of Oceanology and Limnology for improving the English
of the manuscript and giving valuable suggestions. The anonymous reviewers gave constructive comments and suggestions. We thank hardworking of the crew of R/V Science No. 1 for collecting the study samples.
We also appreciate senior engineer Ma Zhibang, Zhang Qin, Deng Yuejin,
and Wang Hongli for great assistance in sample analyses.
2
Asia. Chin J Geophys (in Chinese), 2002, 45(2): 188―197
Xu Z K. Origin and paleoceanographic environments response of
XU ZhaoKai et al. Chinese Science Bulletin | March 2008 | vol. 53 | no. 6 | 923-931
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
Printing Office, 1981. 597―602
Kolla V, Nadler L, Bonatti E. Clay mineral distributions in surface
sediments of the Philippine Sea. Oceano Acta, 1980, 3(2): 245―250
Qin Y S, Chen L R, Shi X F. Research on the eolian sediment in the
West Philippine Sea. Chin Sci Bull (in Chinese), 1995, 40(17):
1595―1597
Greaves M J, Elderfield H, Sholkovitz E R. Aeolian sources of rare earth
elements to the Western Pacific Ocean. Mar Chem, 1999, 68: 31―38
Yang S Y, Li C X. Research progress in REE tracer for sediment
source. Adv Earth Sci (in Chinese), 1999, 14(2): 164―167
German C, Elderfield H. Application of the Ce anomaly as a paleoredox
indicator: the ground rules. Paleoceanography, 1990, 5: 823―833
Liu Y J, Cao L M. General Element Geochemistry (in Chinese). Beijing: Geological Publishing House, 1987. 57―80
Wang X J, Chen Y W, Lei J Q, et al. A study on geochemistry of the
rare earth elements in seafloor sediments in the continental shelf of the
East China Sea. Geochimica (in Chinese), 1982, 1: 56―65
Liu N, Meng X W. Characteristics of rare earth elements in surface
sediments from the middle Okinawa Trough: Implications for provenance of mixed sediments. Mar Geol Quat Geol (in Chinese), 2004
24(4): 37―43
Wen Q Z, Diao G Y, Geng A S, et al. Geochemistry of China Loess (in
Chinese). Beijing: Geological Publishing House, 1989. 1―285
Shen H T. Rare earth elements in deep-sea sediments. Geochimica (in
Chinese), 1990, 4: 340―347
Tian L Y, Zhao G T, Chen Z L, et al. The preliminary study of
petrological geochemistry of basalts from hydrothermal activity regions, Mariana Trough. J Ocean Univ Qingdao (in Chinese), 2003,
33(3): 405―412
Migdisov A A, Miklishansky A Z, Saveliev B V, et al. Neutron activation analysis of rare earth elements and some other trace elements in
volcanic ashes and pelagic clays, Deep Sea Drilling Project Leg 59. In:
Kroenke L, Scott B R, Brassell S, et al. eds. Initial Reports of the Deep
Sea Drilling Project, 59. Washington: U.S. Govt. Printing Office, 1981.
653―668
Sholkovitz E R. Rare earth elements in marine sediments and
chemical standards. Chem Geol, 1990, 88: 333―347
Sholkovitz E R, Landing W M, Lewis B L. Ocean particle chemistry:
the fractionation of rare earth elements between suspended particles
and seawater. Geochim Cosmochim Acta, 1994, 58: 1567―1579
Wang Z G, Yu X Y, Zhao Z H, et al. Geochemistry of Rare Earth
Elements (in Chinese). Beijing: Science Press, 1989. 265―276, 469
Taylor S R. Abundance of chemical elements in the continental crust:
a new table. Geochim Cosmochim Acta, 1964, 28: 1273―1285
Liu B L, Wang Y P, Wang J Z, et al. Geochemical characters of REE in
the seafloor sediment in northern continental slope of the South China
Sea and analysis of source of material and diagenesis environment.
Mar Geol Quat Geol (in Chinese), 2004, 24(4): 17―23
Liu J H, Liang H F, Xia N, et al. REE geochemistry of <2 μm fractions
in deep-sea sediments from East Pacific. Geochimica (in Chinese),
1998, 27(1): 49―58
Scott B R, Kroenke L, Zakariadze G, et al. Evolution of the south
Philippine Sea: Deep Sea Drilling Project Leg 59 results. In: Kroenke
L, Scott B R, Balshaw K, et al., eds. Initial Reports of the Deep Sea
Drilling Project, 59. Washington: U.S. Govt. Printing Office, 1981.
803―815
XU ZhaoKai et al. Chinese Science Bulletin | March 2008 | vol. 53 | no. 6 | 923-931
931
ARTICLES
20
OCEANOGRAPHY
3
ferromanganese crusts (nodules) in the East Philippine Sea. Dissertation for the Doctoral Degree (in Chinese). Qingdao: Institute of
Oceanology, Chinese Academy of Sciences, 2007
Xu Z K, Li A C, Jiang F Q, et al. Paleoenvironment evolution of the
East Philippine Sea recorded in the new-type ferromanganese crust
since the terminal Late Miocene. Sci China Ser D-Earth Sci, 2007,
50(8): 1179―1188
Rea D K, Snoeckx H, Joseph L H. Late Cenozoic eolian deposition in
the North Pacific: Asian drying, Tibetan uplift, and cooling of the
northern hemisphere. Paleoceanography, 1998, 15: 215―224
Sun Y B, Gao S, Li J. Preliminary analysis of grain-size populations
with environmentally sensitive terrigenous components in marginal
sea setting. Chin Sci Bull, 2003, 48(2): 184―187
Piper D Z. Rare earth elements in the sedimentary cycle: A summary.
Chem Geol, 1974, 14: 285―304
Huang Y Y, Yang H N, Kuang Y Q, et al. Controlling of the Formation
and Distribution for Polymetallic Nodules by the Seafloor Sediment
Types and its Geochemical Environment (in Chinese). Wuhan: China
University of Geosciences Press, 1997. 91―104
Xia M. U-series Dating Method and Laboratory Technology (in Chinese). Lanzhou: Lanzhou University Press, 1989
Chen W J, Ji F J, Wang F. Dating on Young Geologic System (continued) (in Chinese). Beijing: Seismological Press, 1999
Ujiié H. Planktonic foraminiferal biostratigraphy in the Western Philippine Sea, Leg 31 of DSDP. In: Karig D E, Ingle J C, Jr, et al. eds.
Initial Reports of the Deep Sea Drilling Project, 31. Washington: U.S.
Govt. Printing Office, 1975. 677―691
Zhao Y Y, Yan M C. Geochemistry of Sediments of the China Shelf
Sea (in Chinese). Beijing: Science Press, 1994
Li F Y, Gao S, Jia J J. Late Quaternary sedimentation rate in the
northern Okinawa Trough. In: Gao S, Li J B, eds. The Formation and
Evolution of Chinese Marginal Seas (in Chinese). Beijing: Ocean
Press, 2002. 140―146
Huang W, Wang P X. Sediment mass and distribution in the South
China Sea since the Oligocene. Sci China Ser D-Earth Sci, 2006,
49(11): 1147―1155
Yan W, Chen M H, Li C D, et al. The sedimentary sequences during
last 30 ka revealed by REE records in core WP92-3 from West Pacific
Warm Pool and their environmental implications. Acta Mineral Sin
(in Chinese), 2006, 26(1): 22―28
Folk R L. A review of grain-size parameters. Sedimentology, 1966, 6:
73―97
Gao S, Jia J J. The grain-size characteristics of the near surface sediment in the Mid-North Okinawa Trough and its vicinities. In: Gao S,
Li J B, eds. The Formation and Evolution of Chinese Marginal Seas
(in Chinese). Beijing: Ocean Press, 2002. 125―139
Zhang F Y, Zhang W Y, Yang Q H. Characteristics of grain size distributions of surface sediments in the Eastern South China Sea. Acta
Sediment Sin (in Chinese), 2003, 26(1): 452―460
Han Y X, Xi X X, Fang X M, et al. Dust storm in Asia continent and
its bio-environmental effects in the North Pacific: A case study of the
strongest dust event in April, 2001 in central Asia. Chin Sci Bull, 2006,
51(6): 723―730
Balshaw M K. Cenozoic clay-mineral stratigraphy in the south Philippine Sea. In: Kroenke L, Scott B R, Brassell S, et al. eds. Initial
Reports of the Deep Sea Drilling Project, 59. Washington: U.S. Govt.